The United States Tuesday called North Korea's threat to withdraw from negotiations and restart its nuclear program a serious step in the wrong direction. Pyongyang has reacted harshly to a U.N. Security Council statement condemning its April 5 missile launch.

Obama administration officials said they don't want to get involved in verbal sparring with North Korea but they did call its latest threats provocative and say Pyongyang stands only to further isolate itself from the world community if it follows through with them.

North Korea said Tuesday it found the U.N. Security Council condemnation of its missile launch an unbearable insult, and said it was withdrawing from the Chinese-sponsored six-party talks on its nuclear program and moving to reopen nuclear facilities shut down under aid-for-disarmament commitments.

The International Atomic Energy Agency, which has been monitoring North Korean nuclear sites, said it had been informed that its inspectors were being expelled.

At the White House, Press Secretary Robert Gibbs said the threatened North Korea moves were "a serious step in the wrong direction" and urged Pyongyang to end what he termed its "provocative threats" and live up to its international obligations.

Reaction was more subdued at the State Department, where Acting Spokesman Robert Wood said Monday's Security Council statement condemning the missile launch and threatening tougher sanctions spoke for itself, and that retaliation would only mean further isolation for Pyongyang.

"The statement was very clear. There was no question about the intent of the statement, what the statement required of the north. This is something that we've been addressing for quite some time," he noted.  "The North as you know has been engaged in all sort of behavior. There have been ups and downs in that entire progress, the six-party talks. As I said the international community spoke very clearly to the north. It was a very strong response and made very clear what the north needs to do," he said.

A senior official here said the administration had anticipated a sharp response by Pyongyang to Monday's Security Council statement and that the United States did not intend to "get bogged down" by responding to every statement carried by the official North Korean media.

North Korea contends the April 5 missile firing was a satellite launch to which it was entitled under international law. U.S. officials said no part of the three-stage vehicle reached orbit, and that in any case it amounted to a long-range ballistic missile test forbidden under a Security Council resolution that followed its October 2006 nuclear test.

North Korea agreed in principle in 2005 to scrap its nuclear program, including a presumed arsenal of several nuclear weapons, in exchange for energy aid and diplomatic benefits. But the six-party talks have stalled over Pyongyang's refusal to accept a verification program for the declaration of its nuclear assets and activities that was agreed to last June.